Rafter principals for use in roofs of large span



A118. 1957 H. MACLAINE PONT 2,802,432

RAFTER PRINCIPALS FOR USE IN ROOFS 0? LARGE SPAN Filed larch 17, 1953 2 Sheets-Sheet 1 1957 H. MACLAINE PONT 2,802,432

RAFTER PRINCIPAL-5' FOR 'USE IN ROOFS 0F LARGE SPAN 2 Sheets-Sheet 2 Filed March 17. 1953 trite The invention relates to a rafter principal fora-roof of largespan 'of the type described in UWS. Patent No. 2,545,556 and comprises, in combination, abutment structures :at the corners .of 1 the roofed space 11 only,:.flexible curved :rafters; which" rest I on said. 1 abutment structures, meet in the top of the roof and areturned withtheir concave sides toward the inside, eavesecables provided round about the roof on theilevel came :lower endssofl'said rafters, networks composed of completely flexibleistretchiable wire-like means provided in the roofing .rplanes between said rafters and said eaves-cables, and a roof covering supported directly by'said roofingnetworks. In such roof structures the danger of buckling 'of their'a fteriprincipals due to the expected efiicient variations of the shape thereof is eliminated. However, the rafter principals must be able to take up great compressive stresses in their longitudinal direction. Moreover they must be adapted to be constructed in very great lengths.

The present invention has for its object to provide for such a roof a rafter principal of simple construction, which fulfils the above mentioned requirements. It resides in that the rafter construction consists of a rigid foot member, a rigid top member and a composite intermediate member, said intermediate member comprising layers of resilient bars, which partly overlie each other and point with their lower ends toward the outside and with their upper ends towards the inside of the rafter principal, and link members, which engage, in a manner permitting the rafter principal to take up compressive strain, with their parts turned toward the outside of said top member and the lower ends of said bars respectively, and with their parts turned toward the inside the upper ends of said bars and said foot member, respectively, the main axes of said bars and said link members enclosing acute angles. This construction makes it possible to compose the matter construction of a great number of bars, which are easily to be manufactured and are automatically pressed one upon the other and together form in each place of the rafter principal .a cross-section of sufficient area to take up the compressive strain set up in the principal, without the flexibility of the construction as a whole being unfavourably affected by the relatively large cross-sectional area thereof.

The rafter construction may be formed in various manners. Preferably the bars are solid, have a square crosssection and are of equal lengths. The link members may consist of blocks and connecting rods, said blocks being engaged by the bars and said rods being at both ends hingedly connected to said blocks.

The bars may be pre-bent according to the thrustline of the rafter construction, when the roof is in its condition of rest. In that case the bending of the rafter construction to the outside and to the inside during the movements of the roof due to the influence of the weather and the like depends on the elasticity of the bars, which then always form a rigid unit irrespective of the movements of States Patent Ofifice 2,802,432 Patented Aug. 13, 1957 the rafterconstruction. Only one kind of link isthen needed.

The bars mayalso be straight bars. In the case, however, thespaces left open between the bars, when the foot ends or other particular points of the bars follow the thrustline referred to, will have to be filled up with filling or distance blocks. -Advantageously these filling or dis tance blocks are mounted in the interspaces near the con- 'n'ecting rodsof the link members. In that case the said rodswill have to'be of various lengths. However, if the link'members are made adjustable, only a few types of connecting rods are needed. Also then thevariations of the form ofthe rafter construction owing to the varying 'load depend on the elasticity of the bars.

The construction of the rafter structure according to the inventionhas the advantage, that the mounting of the structureis rather simple, especially when large spans are concerned. -The use of section iron and riveting and welding processesare substantially dispensed with ma structureaccording to the invention.

The blocks-ofthelink-members may be formed and engage 'eaich other'= in=such -a -manner,that they form a continuous'outer layer or an uninterrupted inner layer of the rafter structure, when the latter attains a predeter- "mined minimally ormaximally bent position, respectively, :vduring the movements of the roof for restoring the :-:equilibrium. 'Theser-bl'ocksthen engage'each other and locally enlarge the cross-sectional area of the rafter structure, so that the latter is proof against greater compressive strain. These additional compression zones are not operative, when loads occur within the range, which will have to be considered in the calculation of the construction in connection with the weather statistics and the building regulations. Only, when extreme weather conditions or other catastrophes occur, will they be active.

The accompanying drawing illustrates diagrammatically and by way of example one embodiment of a rafter principal according to the invention and wherein:

Fig. 1 is a diagrammatical elevational view of a rafter principal for an elastic roof of large span,

Fig. 2a on a larger scale the foot portion of said rafter principal,

Fig. 2b is on a larger scale the top portion of said rafter principal, and

Fig. 3 is a cross-sectional view on line III-III in Fig. 2a.

In the drawings 1 designates a foot-member and 2 is .a top-member of the rafter principal. These members form the ends of the rafter principal and they are of rigid construction and may be made of cast or Wrought metal. The foot-member 1 bears through a universal joint on a spherical foot 3, which bears with its spherical sole surface 4 on a surface 6 of a stationary support through balls 5. The illustrated rafter structure forms a part of an elastic roof provided with spherical foot supports as described in the copending U. S. patent application Serial No. 210,510, new Patent No. 2,705,928.

The intermediate part of the rafter structure, that is the part extending between the foot-member 1 and the top-member 2, i composed of layers of bars 8 lying one beside the other. These layers overlap each other at their adjoining upper and lower ends. Thus, the bars of the first layer, which are joined at their upper ends to the top member, overlap, at their lower ends, the upper ends of the next or second layer of bars in such a manner that a link means connecting the bars of the layers, and the bars enclose acute angles. This construction follows for succeeding layers down to the lowermost layer of bars which is joined to the foot member. Said bars abut with their outward and footward pointing ends against blocks 9 through interposed cross-bars 8a and they engage blocks with their inward and topward pointing ends. The

blocks 9 and the top-member 2 are hingedly connected with the foot-member, the block 10 and intermediate blocks 10a, respectively, -by means of link-rods fl- 1. To

this end the link-rods 11 are pivotally connected with their outward pointing ends to the blocks 9 and the top- 7 member 2, respectively, and with their inward pointing ends they are passed through cross-beams 12 and fixed by means of nuts 13 or they are pivotally connected to the foot-member. Each of the cross-beams engages, with nected to the link-rods 11 by means of braces 17. The

link-rods 11 and the bars 8, which are interconnected by said rods, enclose acute angles. The bars 8 are pressed upon each other or upon the interposed blocks 16 by the weight of the roof-covering supported by the rafter principal. The blocks 9 and 10, 10a are so formed and of such dimensions, as to abut against each other or to engage each other in the manner of books, when, during the movements of the roof for restoring the equilibrium, the rafter principals attain the minimum or the maximum curvatures to be expected, respectively.

Each horizontal row of blocks 9 may be connected to a horizontal row of blocks 10 and a horizontal row of blocks 10w by means of two rows of link-rods 11. In

the present construction the flexibility of the rafter principal depends on the elasticity of the bars.

What I claim is:

1. A rafter structure for a roof of large span consisting of a rigid foot member, a rigid top member and a composite intermediate member disposed between the foot member and the top member, said intermediate member comprising layers of resilient bars, said layers being inclined between the top member and the foot member and pointing with their lower ends toward the outside and with their upper ends toward the inside of the curve of the rafter structure and said layers having their lower ends overlapping the upper ends of adjoining lower layers, link means connecting the uppermost layers with the top member and the lowermost layers with the foot member and connecting the lower end of an intermediate layer with the underlying upper end of an adjoining intermediate layer, the longitudinal axes of the bars of said layers and the link means enclosing acute angles.

2. A rafter structure as claimed in claim 1, wherein the link means includes blocks at the upper and lower ends of the bars and connecting rods hingedly connected 7 at both endsto the blocks.

3. A rafter structure as claimed in claim 1, wherein distance-pieces are locally provided between the bars of adjoining layers.

References Cited in the file of this patent UNITED STATES PATENTS 2,237,226 High Apr. 1, 1941 

